Two elements are studied. One has atomic number X and one has atomic number X+2. It is known that element X is a halogen. To what group does the X+2 element belong?

Group 1 (or IA)

Explanation:

If element X is a halogen, then it belongs to the group 17 (or VIIA, under a different notation).

For each extra unit of atomic number, the group number increases by 1. That means that the X+1 element would belong to the group 18 (or VIIIA). The X+2 element would thus belong in the group 1 (or IA) one period higher (higher as in numeric value, not as in position in the periodic table).

indium, and thallium have three electrons i think

a rain shadow is a dry region of land on the side that is protected against the prevailing winds of a mountain range. the prevailing winds are the winds that occur most of the time in a particular place of the earth

prevailing winds carry air toward the mountain range. as the air rises up over a mountain range, the air cools, water vapor condenses, and clouds form. on this side of the mountains, called the windward side, precipitation falls in the form of  rain  or snow. this dry air produces a  rain shadow.